Method for constant power density scaling

ABSTRACT

A method for constant power density scaling in MOSFETs is provided. A method for manufacturing an integrated circuit includes computing fixed scaling factors for a first fabrication process based on a second fabrication process, computing settable scaling factors for the integrated circuit to be fabricated using the first fabrication process, determining parameters of the integrated circuit based on the settable scaling factors, and manufacturing the integrated circuit using the determined parameters. The first fabrication process creates devices having a smaller device dimension than the second fabrication process and the settable scaling factors are set based on the fixed scaling factors.

This application claims the benefit of U.S. patent application Ser. No.12/828,591, filed on Jul. 1, 2010, entitled “Method for Constant PowerDensity Scaling,” which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/239,335, filed on Sep. 2, 2009, and entitled“Method for Constant Power Density Scaling,” both of which applicationsare incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to integrated circuits, andmore particularly to MOSFETs.

BACKGROUND

Silicon CMOS device technology has shrunken device dimensions by morethan an order of magnitude, and is expected to continue to shrink devicedimensions down into the sub-5 nm range within the decade. Whilecontinuing advances in manufacturing has enabled the reduction in devicedimensions, device scaling poses serious challenges at the circuit andsystem levels. Challenges include reduced power supply voltages,increased leakage currents, decreased reliability, and severelyincreased power density of integrated systems.

FIG. 1 illustrates data plots of power supply voltage level versusdevice dimension (shown as trace 105) and power density versus devicedimension (shown as trace 110). As device dimensions shrunk from about0.5 um down to about 0.13 um (shown in span 115), a technique known asconstant field scaling was used to scale power supply voltage levelalong with the shrinking device dimensions. In constant field scaling,the power supply voltage levels scale in proportion with the devicedimension. An added bonus with constant field scaling as devicedimensions shrunk from 0.5 um to 0.13 um is that power density remainedsubstantially constant.

Then, as device dimensions shrunk from about 130 nm down to about 32 nm(shown as span 120), constant field scaling was no longer effective,since the rapid drop in power supply voltage levels made integratedcircuits susceptible to noise and presented reliability issues. Instead,power supply voltage levels were kept nearly constant while drivecurrent per device width increased. Performance boosters, such asstrained substrate technology, and so forth, were used to help increasedrive current per device width. The nearly constant power supply voltagealong with increased drive current per device width has led to adramatic increase in power density, which may lead to problems such asheat dissipation from the integrated circuit as well as potentiallydecreased device life due to overheating.

Clearly, the drastic increase in power density may not be able tocontinue as device dimensions continue to shrink down to 32 nm and below(shown as span 125) due to heat related problems. Ideally, the powerdensity should remain constant or even decrease as device dimensionscontinue to decrease (shown as trace 130). In order to achieverelatively constant power density, it may be necessary to reduce powersupply voltage levels (shown as trace 135).

SUMMARY

In accordance with an embodiment, a method for manufacturing anintegrated circuit is provided. The method includes computing fixedscaling factors for a first fabrication process based on a secondfabrication process, computing settable scaling factors for theintegrated circuit to be fabricated using the first fabrication process,determining parameters of the integrated circuit based on the settablescaling factors; and manufacturing the integrated circuit using thedetermined parameters. The first fabrication process creates deviceshaving a smaller device dimension than the second fabrication process,and the settable scaling factors are set based on the fixed scalingfactors.

In accordance with another embodiment, a method for manufacturing anintegrated circuit is provided. The method includes providing a designfor the integrated circuit, changing the design to a second fabricationprocess, computing settable scaling factors for the integrated circuitbased on the first fabrication process and the second fabricationprocess, setting integrated circuit parameters based on the settablescaling factors, and manufacturing the integrated circuit using the setintegrated circuit parameters. The design is based on a firstfabrication process.

In accordance with another embodiment, a method for manufacturing anintegrated circuit is provided. The method includes receiving a designfor the integrated circuit based on a first fabrication process,receiving fabrication process based parameters based on the firstfabrication process and a second fabrication process, generating alayout for the design based on the second fabrication process,performing a design rule check on the layout using second fabricationprocess design rules, and fabricating the integrated circuit using thesecond fabrication process.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the embodiments that follow may be better understood.Additional features and advantages of the embodiments will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiments disclosed may be readily utilized as a basisfor modifying or designing other structures or processes for carryingout the same purposes of the present invention. It should also berealized by those skilled in the art that such equivalent constructionsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a data plot of power supply voltage level and power densityversus device dimension;

FIG. 2 is a plot of drive current per device width scaling factor versuspower supply voltage level scaling factor;

FIG. 3 a is a flow diagram of operations in the computing of settablescaling factors;

FIG. 3 b is a flow diagram of operations in the computing of fixedscaling factors;

FIG. 4 is a flow diagram of operations in the scaling of an existingintegrated circuit design; and

FIG. 5 is a flow diagram of operations in the manufacturing of anintegrated circuit.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments are discussed in detail below.It should be appreciated, however, that the present disclosure providesmany applicable inventive concepts that can be embodied in a widevariety of specific contexts. The specific embodiments discussed aremerely illustrative of specific ways to make and use the invention, anddo not limit the scope of the invention.

The embodiments will be described in a specific context, namelyintegrated circuits fabricated using a fabrication process having devicedimensions of 22 nm. The embodiments may also be applied, however, tofabrication processes with other device dimensions, such as 15 nm, 10nm, 7 nm, 5 nm, and so forth. Furthermore, the embodiments may beapplied to fabrication processes with device dimensions greater than 22nm.

As fabrication processes advance and device dimensions decrease, thechange in fabrication processes may be described with several scalingfactors. Some of the scaling factors may be based on the fabricationprocesses themselves and may be fixed. A first exemplary fixed scalingfactor is an area scaling factor k_(A) and may be defined by a scalingof a specified circuit block, such as an IP block, when compared to asimilar circuit block fabricated using a different fabrication process.A second exemplary fixed scaling factor is a delay scaling factor k_(t)and may be defined as a ratio of delays between the fabricationprocesses. For example, the delay scaling factor k_(t) may be defined asa ratio of the intrinsic delay of a device fabricated using thedifferent fabrication processes. Alternatively, the delay scaling factork_(t) may be defined as a ratio of the delay of a circuit fabricatedusing the different fabrication processes.

Other scaling factors may be set by circuit designers as well as beingbased on the fixed scaling factors. A first exemplary settable scalingfactor is a power supply voltage level scaling factor k_(V) and may bedefined as a ratio of power supply voltage levels between thefabrication processes. A second exemplary settable scaling factor is adrive current per device width scaling factor k_(I) and may be definedas a ratio of drive current per device width between the fabricationprocesses. The values used in determining the settable scaling factorsmay be empirical values measured from actual circuits and/orsimulations.

The scaling factors (both the fixed scaling factors and the settablescaling factors) may have an impact on overall performance, powerconsumption, power density, and so forth, of circuits fabricated usingthe fabrication process. Since the fixed scaling factors are dependenton the fabrication processes and typically cannot be changed once thefabrication processes are set, the settable scaling factors may betweaked by circuit designers to achieve desired circuit characteristics.

FIG. 2 illustrates a plot of drive current per device width scalingfactor (k_(I)) versus power supply voltage level scaling factor (k_(V))as device dimension decreases. A straight diagonal line 205 represents aline of constant performance achieved with the same amount of scaling ofthe drive current per device width and power supply voltage level. Acurved line 210 represents a curve of constant power density. If thedrive current per device width and the power supply voltage level arescaled so that they fall upon curved line 210, power density remainsconstant.

A first point 215 located at (1, 1) represents no scaling of either thedrive current per device width or the power supply voltage level. Withthe drive current per device width scaling factor at 1, no drive currentper device width scaling occurs as device dimensions decrease.Similarly, with the power supply voltage level scaling factor at 1, nopower supply voltage level scaling occurs as device dimensions decrease.Even with no scaling of either the drive current per device width orpower supply voltage level, FIG. 2 shows that the power density willincrease as the device dimensions decrease with no change in overallperformance. This may be due to an increase in device density per unitarea resulting from the decrease in device dimensions, i.e., moredevices are packed into the unit area.

A second point 220 located at (0.9, 1.2) represents a scaling of boththe drive current per device width and the power supply voltage level,wherein the power supply voltage level is slightly decreased while thedrive current per device width is increased. Second point 220 representsdrive current per device width and power supply voltage level scalingthat is typical of process scaling occurring today. While yielding asignificant increase in overall performance, there is also a dramaticincrease in power density, which may lead to power related problemsdiscussed previously.

A third point 225 located at (0.84, 0.84) represents a scaling of boththe drive current per device width and the power supply voltage level,wherein both the power supply voltage level and the drive current perdevice width are decreased by an equal amount. Decreasing (orincreasing) both the drive current per device width and the power supplyvoltage level by equal amounts maintains the same overall performance asdevice dimensions decrease. As shown in FIG. 2, scaling the drivecurrent per device width and the power supply voltage level by 0.84 alsoresults in maintaining a constant power density as device dimensionsdecrease. The scaling factor of 0.84 may be dependent on particularfabrication process parameters and may differ for different fabricationprocesses. Therefore, the discussion of 0.84 should not be construed asbeing limiting to either the scope or the spirit of the embodiments.

A fourth point 230 located at (0.7, 1) represents a scaling of just thepower supply voltage level. Fourth point 230 may be illustrative ofconstant field scaling discussed previously. Although it is possible toincrease overall performance and maintain constant power density by justscaling the power supply voltage level, it may be necessary tosignificantly decrease the power supply voltage level. This may lead toreliability and functionality problems as the power supply voltage levelapproaches electrical ground.

A region 235 represents a desirable region wherein a measurable overallperformance increase is achieved with minimum scaling of both the powersupply voltage level and the drive current per device width.Additionally, power density is decreased. Although shown as a circle,region 235 may be irregularly shaped and may be dependent on thefabrication processes involved.

FIG. 3 a illustrates a flow diagram of operations 300 in computing ofsettable scaling factors. Operations 300 may be descriptive of stepsoccurring during the computing of settable scaling factors for use indesigning and manufacturing an integrated circuit. Operations 300 may bebased on a first fabrication process that will be used to fabricate theintegrated circuit and a second fabrication process that will be used asa reference fabrication process. Generally, the first fabricationprocess may be a fabrication process that potentially is still underdevelopment or has just been released for fabrication of high-priced,high-performance integrated circuits. While the second fabricationprocess may be a well-tested, well-characterized process. For example,the second fabrication process may be a fabrication process being usedfor fabricating integrated circuits to be sold for general consumption.Typically, device dimensions producible by the first fabrication processwill be smaller than device dimensions producible by the secondfabrication process.

Operations 300 may begin with determining fixed scaling factors based onthe first fabrication process and the second fabrication process (block305). As discussed previously, fixed scaling factors may include an areascaling factor k_(A) and a delay scaling factor k_(t). The area scalingfactor k_(A) may be determined by comparing similar (or the same)circuit blocks as implemented using the first fabrication process andthe second fabrication process. For example, if the first fabricationprocess has a device dimension of 22 nm and the second fabricationprocess has a device dimension of 45 nm, then the area scaling factork_(A) may be 22/45 or about 0.49. The delay scaling factor k_(t) may bedetermined by comparing delays through similar (or the same) devices orcircuit blocks. For example, an intrinsic delay through an inverter isabout 2.5 ps when the inverter is fabricated using the first fabricationprocess and about 5 ps when the inverter is fabricated using the secondfabrication process, then the delay scaling factor k_(t) may be 2.5/5 orabout 0.50. FIG. 3 b illustrates a flow diagram of operations 350 incomputing fixed scaling factors for the first fabrication process andthe second fabrication process.

Returning now to FIG. 3 a, after computing the fixed scaling factors,the settable scaling factors may be computed (blocks 310 and 315).Relationships between the fixed scaling factors and the settable scalingfactors so that the settable scaling factors fall within a desirableregion, such as region 235 of FIG. 2, may be expressed as:

${{k_{V} \cdot k_{I}} \leq {\sqrt{k_{A}} \cdot k_{t}}},{and}$${\frac{k_{V}}{k_{I}} \leq k_{t}},$where k_(I) is the drive current per device width scaling factor, k_(V)is the power supply voltage level scaling factor, k_(A) is the areascaling factor, and k_(t) is the delay scaling factor. The tworelationships may be combined to solve for k_(V), which may be expressedas:

$k_{V} \leq {\sqrt[4]{k_{A}} \cdot {k_{t}.}}$A detailed description of the relationships is provided below.

Let the power per gate or per logic cell be defined asP=I _(DSAT) ·V _(DD).where I_(DSAT) is the drain saturation current and V_(DD) is the powersupply voltage level. The power density may then be defined as

${{P.D.} = {{\frac{I_{DSAT} \cdot V_{DD}}{Area} \propto \frac{I_{DSAT} \cdot V_{DD}}{W \cdot L}} = {\frac{I_{DSAT}}{W} \cdot \frac{V_{DD}}{L}}}},$where W is transistor width or standard cell height and L is transistorgate dimension or standard cell width.

Constant power density may be achieved by scaling V_(DD) with a scalingconstant k, expressible as:

${{P.D.} \propto \frac{I_{DSAT} \cdot V_{DD}}{W \cdot L}} = {{\frac{I_{DSAT}}{W} \cdot \frac{V_{DD}}{L}} = {{( {\frac{I_{DSAT}}{W} \cdot V_{DD}} ) \cdot k}\frac{1}{L \cdot k}}}$The scaling of V_(DD) with the scaling constant k is known as constantfield scaling, as discussed above.

Alternatively, constant power density scaling may be achieved by scalingthe product

$\frac{I_{DSAT}}{W} \cdot V_{DD}$with the scaling constant k. When the above equation is satisfied, thepower density remains constant, but potentially with a different delay.

Intrinsic delay t is expressible as:

${{t \propto \frac{C_{OX} \cdot W \cdot L \cdot V_{DD}}{I_{DSAT}}} = {{L \cdot k \cdot \frac{1}{T_{inv} \cdot k}}\frac{V_{DD}}{( \frac{I_{DSAT}}{W} )}}},$where C_(OX) is gate oxide capacitance and T_(inv) is equivalent gateoxide thickness.

Since a minimum requirement is no delay degradation, it is needed that

$\frac{V_{DD}}{( \frac{I_{DSAT}}{W} )}$does not scale.

Therefore, it can be shown that the minimum requirement for the powersupply voltage level scaling factor is √{square root over (k)}. This maybe referred to as constant delay scaling.

The target drive current per device width and the power supply voltagelevel may then be set using the settable scaling factors (block 320 and325). Operations 300 may then terminate.

As an example, for fabrication processes with device dimensions smallerthan 130 nm, including but not limited to fabrication processes withdevice dimensions of 45 nm and 22 nm, circuits may be implemented withan area scaling factor k_(A) and a delay scaling factor k_(t). Based onthe two fixed scaling factors, a power supply voltage scaling factork_(V) may a scaled down by the area scaling factor, and may be expressedas:

${0.9 \times \sqrt[4]{k_{A}}} \leq k_{V} \leq \sqrt[4]{k_{A}}$With the exception of fabrication processes with device dimensions of130 nm and 90 nm, the above specified power supply voltage level scalingfactor was not used since it violated either the lower bound (between0.5 um and 0.13 um) or the upper bound (between 0.13 um and 32 nm).

Also based on the two fixed scaling factors, a drive current per devicewidth scaling factor k_(I) may scale up by the area scaling factor, andmay be expressed as:

$\sqrt[4]{k_{A}} \leq k_{l} \leq {1.1 \cdot \sqrt[4]{k_{A}}}$

FIG. 4 illustrates a flow diagram of operations 400 in the scaling of anexisting integrated circuit design between a first fabrication processand a second fabrication process. Operations 400 may be based on a firstfabrication process that will be used to fabricate the integratedcircuit and a second fabrication process that will be used as areference fabrication process. The first fabrication process may be usedto create devices with a smaller device dimension than the secondfabrication process.

Operations 400 may begin with receiving a circuit design of anintegrated circuit that is to be scaled (block 405). The circuit designmay include a layout, a netlist, and so forth, of the integrated circuitthat meets the design rules and other requirements of the secondfabrication process. The circuit design may also include references todesign libraries specific to the second fabrication process. The circuitdesign may then be scaled to the first fabrication process parameters(block 410).

The scaling of the circuit design may include simply resizing portionsof the circuit design, as well as re-designing or altering portions ofthe circuit design that may not be amenable to being resized.Additionally, the design libraries specific to the second fabricationprocess may be replaced with a design library specific to the firstfabrication process. The techniques involved in the scaling of a circuitdesign are considered to be well known by those of ordinary skill in theart of the embodiments and will not be discussed further herein.

Additionally, settable scaling factors, such as a power supply voltagelevel scaling factor k_(V) and a drive current per device width scalingfactor k_(I), may be set based on fixed scaling factors (area scalingfactor k_(A) and delay scaling factor k_(t), for example) (block 415).As discussed previously, fixed scaling factors are based on physicaldifferences between the first fabrication process and the secondfabrication process, such as device dimension, propagation delay, and soforth. Settable scaling factors may specify parameters of the integratedcircuit and may have an impact on the performance of the integratedcircuit.

Circuit parameters, such as power supply voltage level and normalizedsaturation current, may also be set (block 420). The circuit parametersmay be set based on settable scaling factors, such as power supplyvoltage level scaling factor k_(V) and drive current per device widthscaling factor k_(I). The circuit parameters may be set as a function ofsimilar circuit parameters for the circuit design when fabricated usingthe second fabrication process. For example, when transitioning from afabrication process with 45 nm device dimensions to a fabricationprocess with 22 nm device dimensions, the power supply voltage level mayrange from about 0.9 to about 1.0 times a fourth-root of the areascaling factor k_(A) of the two fabrication processes. Similarly, drivecurrent per device width may range from about 1.0 to about 1.1 times thefourth-root of the area scaling factor k_(A).

With the circuit design scaled and circuit parameters adjusted, thecircuit design may be tested (block 425). Testing of the circuit designmay include simulations to verify correctness of the circuit design, aswell as testing to ensure that parameters, such as power consumption,delays, and so forth, of the circuit are met. If the circuit designpasses testing, then the circuit design operations 400 may thenterminate. If the circuit design does not pass testing, thenmodifications to the circuit design may be needed.

FIG. 5 illustrates a flow diagram of operations 500 in the manufactureof an integrated circuit. Operations 500 may make use of differences,such as differences in area, delay, and so forth, between a firstfabrication process and a second fabrication process to help manufacturethe integrated circuit so that the integrated circuit meets designcriteria. Examples of design criteria include better overallperformance, lower power density, lower power consumption, and so forth.The first fabrication process may be capable of producing devices with asmaller device dimension than the second fabrication process.

Operations 500 may begin with a circuit design (block 505). The circuitdesign may be an existing design or a new design. Fabrication processbased parameters may be provided (block 510). Fabrication process basedparameters may include fixed scaling factors, such as an area scalingfactor k_(A) and a delay scaling factor k_(t), and settable scalingfactors, such as a power supply voltage level scaling factor k_(V) and adrive current per device width scaling factor k_(I), which may be basedon the fixed scaling factors and specified performance criteria. Thefixed scaling factors may be computed a priori and stored for subsequentuse in, e.g., a computer readable medium, while the settable scalingfactors may be computed as needed. The settable scaling factors may alsobe based on performance requirements of the integrated circuit, such asoverall performance, power density, power consumption, powerdissipation, and so forth. The fabrication process based parameters maybe used to specify circuit characteristics, such as power supply voltagelevel, drive current per device width, and so forth. The fabricationprocess based parameters may have an impact on the circuit design.

The circuit design, in combination with the fabrication process basedparameters, may then be used to create a circuit layout (block 515). Thecircuit layout may be created using a place and route application, forexample. A design rule check may then be performed to help ensure thatthe circuit layout satisfies the design rules of the first fabricationprocess (block 520). A comparison between the final circuit design(circuit layout) to original design specifications (schema) may beperformed to help ensure that the circuit design fully matches theoriginal design. The comparison may be performed by using SPICE, forexample. The circuit design may then be fabricated (block 530). Afterfabrication, the manufacture of the circuit may continue with testing ofthe fabricated integrated circuits, dicing, packaging, and so forth.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method of manufacturing a circuit, the methodcomprising: receiving a design for an integrated circuit based on afirst fabrication process, the design comprising at least a reference toat least one first design library associated with the first fabricationprocess; scaling, by resizing, physical dimensions of a first part ofthe integrated circuit comprising scalable circuit elements resizablefor fabrication according to a second fabrication process creatingdevices having a smaller device dimension than the first fabricationprocess; altering a second part of the integrated circuit comprisingun-scalable circuit elements non-amenable to resizing for fabricationaccording to the second fabrication process, altering comprisingchanging a design of the second part of the integrated circuit;computing at least one settable scaling factor for the integratedcircuit with a power density of the integrated circuit remainingsubstantially constant or decreasing, the at least one settable scalingfactor based on a feature of the integrated circuit fabricated accordingto the first fabrication process in relation to a feature of theintegrated circuit fabricated according to the second fabricationprocess, the at least one settable scaling factor further based on atleast one fixed scaling factor that is based on the fabricationprocesses and indicating a ratio of a feature of the integrated circuitfabricated according to a first fabrication process to a feature of theintegrated circuit fabricated according to a second fabrication process;setting, by using a computer, integrated circuit parameters based on theat least one settable scaling factor; and manufacturing the integratedcircuit using the integrated circuit parameters; wherein the at leastone fixed scaling factor further comprises an area scaling factor,wherein the at least one fixed scaling factor further comprises at leasta delay scaling factor and wherein the at least one settable scalingfactor further comprises a voltage level scaling factor, and wherein arelationship between the voltage level scaling factor and the at leastone fixed scaling factor is expressible as$k_{V} \leq {\sqrt[4]{k_{A}} \cdot {k_{t}.}}$ where k_(V) is the voltagelevel scaling factor, k_(A) is the area scaling factor, and k_(t) is thedelay scaling factor.
 2. The method of claim 1, wherein the at least onesettable scaling factor further comprises a drive current per devicewidth scaling factor.
 3. The method of claim 2, wherein a relationshipbetween the drive current per device width scaling factor and the atleast one fixed scaling factor is expressible as${\frac{k_{V}}{k_{I}} \leq k_{t}},$ where k_(V) is the voltage levelscaling factor, k_(I) is the drive current per device width scalingfactor, and k_(t) is the delay scaling factor.
 4. The method of claim 2,wherein the at least one fixed scaling factor further comprises an areascaling factor, and wherein the at least one settable scaling factorfurther comprises a voltage level scaling factor, and wherein arelationship between the voltage level scaling factor and the at leastone fixed scaling factor is expressible as $k_{V} \leq \sqrt[4]{k_{A}}$where k_(V) is the voltage level scaling factor and k_(A) is the areascaling factor.
 5. The method of claim 1, wherein the area scalingfactor is proportional to a ratio of a first minimum device dimension ofa device created using the first fabrication process to a second minimumdevice dimension of a device created using the second fabricationprocess.
 6. The method of claim 1, wherein the at least one settablescaling factor further comprises a drive current per device widthscaling factor.
 7. The method of claim 6, wherein a relationship betweenthe drive current per device width scaling factor and the at least onefixed scaling factor is expressible as${\frac{k_{V}}{k_{I}} \leq k_{t}},$ where k_(V) is the voltage levelscaling factor, k_(I) is the drive current per device width scalingfactor, and k_(t) is the delay scaling factor.
 8. A method ofmanufacturing an integrated circuit, the method comprising: determiningat least one settable scaling factor for the integrated circuit to befabricated using a first fabrication process, wherein the at least onesettable scaling factor indicates an operating characteristic of afeature of the integrated circuit to be fabricated according to thefirst fabrication process, and wherein the at least one settable scalingfactor is computed based on at least one fixed scaling factor while apower density of the integrated circuit remains substantially constantor decreasing; determining parameters, by using a computer, of theintegrated circuit to be fabricated according to a second fabricationprocess and based on the at least one settable scaling factor; andmanufacturing the integrated circuit using the parameters; wherein theat least one fixed scaling factor indicates a ratio of a feature of theintegrated circuit fabricated according to a first fabrication processto a feature of the integrated circuit fabricated according to a secondfabrication process, wherein the fixed scaling factors are based on thefabrication processes, wherein the first fabrication process createsdevices having a smaller device dimension than the second fabricationprocess; and wherein the at least one fixed scaling factor comprises atleast a delay scaling factor based on the delay of an integrated circuitfabricated according to the first and second fabrication processes;wherein the at least one fixed scaling factor further comprises an areascaling factor based on the area of an integrated circuit fabricatedaccording to the first and second fabrication processes; wherein the atleast one settable scaling factor further comprises a voltage levelscaling factor indicating a ratio of power supply voltage levels betweena device fabricated according to the first and second fabricationprocesses and a drive current per device width scaling factor indicatinga ratio of drive current per device width between a device fabricatedaccording to the first and second fabrication processes; and wherein arelationship between the voltage level scaling factor and the at leastone fixed scaling factor is expressible as:${k_{V} \leq {\sqrt[4]{k_{A}} \cdot k_{t}}},$ where k_(V) is the voltagelevel scaling factor, k_(A) is the area scaling factor, and k_(t) is thedelay scaling factor.
 9. The method of claim 8, wherein the area scalingfactor is proportional to a ratio of a first minimum device dimension ofa device created using the first fabrication process to a second minimumdevice dimension of a device created using the second fabricationprocess.
 10. The method of claim 8, wherein the delay scaling factor isproportional to a ratio of a single device delay of a device createdusing the first fabrication process to a single device delay of a devicecreated using the second fabrication process.
 11. The method of claim 8,wherein the voltage scaling factor is smaller than a fourth-root of thearea scaling factor.
 12. The method of claim 8, wherein a devicedimension of the first fabrication process is 22 nm and a devicedimension of the second fabrication process is 45 nm, and wherein thevoltage scaling factor is chosen from a range of about 0.9 to about 1.0times a fourth-root of the area scaling factor.
 13. The method of claim8, wherein a relationship between the voltage level scaling factor, thedrive current per device width scaling factor, and the fixed scalingfactors are expressible as: ${\frac{k_{V}}{k_{I}} \leq k_{t}},$ wherek_(V) is the voltage level scaling factor, k_(I) is the drive currentper device width scaling factor, and k_(t) is the delay scaling factor.14. A method of manufacturing an integrated circuit, the methodcomprising: determining at least one settable scaling factor for theintegrated circuit to be fabricated using a first fabrication process,wherein the at least one settable scaling factor indicates an operatingcharacteristic of a feature of the integrated circuit to be fabricatedaccording to the first fabrication process, and wherein the at least onesettable scaling factor is computed based on at least one fixed scalingfactor while a power density of the integrated circuit remainssubstantially constant or decreasing; determining parameters, by using acomputer, of the integrated circuit to be fabricated according to asecond fabrication process and based on the at least one settablescaling factor; and manufacturing the integrated circuit using theparameters; and wherein the at least one fixed scaling factor comprisesat least a delay scaling factor based on the delay of an integratedcircuit fabricated according to the first and second fabricationprocesses; wherein the at least one settable scaling factor furthercomprises a voltage level scaling factor indicating a ratio of powersupply voltage levels between a device fabricated according to the firstand second fabrication processes and a drive current per device widthscaling factor indicating a ratio of drive current per device widthbetween a device fabricated according to the first and secondfabrication processes; and wherein a relationship between the voltagelevel scaling factor, the drive current per device width scaling factor,and the fixed scaling factors are expressible as:${\frac{k_{V}}{k_{I}} \leq k_{t}},$ where k_(V) is the voltage levelscaling factor, k_(I) is the drive current per device width scalingfactor, and k_(t) is the delay scaling factor.
 15. The method of claim14, wherein the drive current per device width scaling factor is largerthan a fourth-root of the area scaling factor.
 16. The method of claim14, wherein a device dimension of the first fabrication process is 22 nmand a device dimension of the second fabrication process is 45 nm, andwherein the drive current per device width scaling factor is chosen froma range of about 1.0 to 1.1 times a fourth-root of the area scalingfactor.
 17. The method of claim 14, wherein determining parameterscomprises: setting a power supply voltage to be substantially equal to apower supply voltage used for an integrated circuit fabricated using thesecond fabrication process multiplied by the voltage level scalingfactor; and setting a target drive current per device width to besubstantially equal to a target drive current per device width of theintegrated circuit fabricated using the second fabrication processmultiplied by the drive current per device width scaling factor.
 18. Themethod of claim 14, wherein the at least one fixed scaling factorcomprises an area scaling factor which indicates a ratio of an area of afeature of the integrated circuit fabricated according to a firstfabrication process to a feature of the integrated circuit fabricatedaccording to a second fabrication process.
 19. The method of claim 18,wherein the area scaling factor is proportional to a ratio of a firstminimum device dimension of a device created using the first fabricationprocess to a second minimum device dimension of a device created usingthe second fabrication process.
 20. The method of claim 14, wherein thedetermining the at least one fixed scaling factor comprises retrievingat least one fixed scaling factor retrieved from storage.